New CadSoft EAGLE DRU files for EAGLE V6

Introduction to CadSoft EAGLE and DRU Files

CadSoft EAGLE (Easily Applicable Graphical Layout Editor) is a powerful and user-friendly electronic design automation (EDA) software used for designing printed circuit boards (PCBs). It is widely used by engineers, hobbyists, and students for creating professional-grade PCB layouts. One of the key features of CadSoft EAGLE is its Design Rule Check (DRC) functionality, which ensures that the PCB design adheres to a set of predefined design rules. These design rules are stored in Design Rules (DRU) files, which are essential for maintaining the integrity and manufacturability of the PCB.

With the release of EAGLE V6, CadSoft has introduced new DRU files that offer enhanced capabilities and improved design rule management. In this article, we will explore the new CadSoft EAGLE DRU files for EAGLE V6, their features, and how they can help you create better PCB designs.

What are CadSoft EAGLE DRU Files?

CadSoft EAGLE DRU files are plain text files that contain a set of design rules for PCB layouts. These rules define the constraints and requirements for various aspects of the PCB design, such as minimum trace width, minimum clearance between components, drill sizes, and more. DRU files help ensure that the PCB design is manufacturable and meets the required specifications.

When you run the Design Rule Check (DRC) in EAGLE, it compares your PCB layout against the rules defined in the selected DRU file. If any violations are found, EAGLE will highlight them, allowing you to make necessary corrections to your design.

Structure of a DRU File

A typical CadSoft EAGLE DRU file consists of several sections, each defining a specific set of design rules. Here’s a basic structure of a DRU file:

description[string]
layerSetup[string]
mtCopper = N
mtIsolate = N
mdWireWire = N
mdWirePad = N
mdWireVia = N
mdPadPad = N
mdPadVia = N
mdViaVia = N
mdSmdPad = N
mdSmdVia = N
mdSmdSmd = N
mdViaViaSameLayer = N
mnLayersViaInSmd = N
mdCopperDimension = N
mdDrill = N
mdSmdStop = N
msWidth = N
msDrill = N
msMicroVia = N
msBlindViaRatio = N
rvPadTop = N
rvPadInner = N
rvPadBottom = N
rvViaOuter = N
rvViaInner = N
rvMicroViaOuter = N
rvMicroViaInner = N
rlMinPadTop = N
rlMaxPadTop = N
rlMinPadInner = N
rlMaxPadInner = N
rlMinPadBottom = N
rlMaxPadBottom = N
rlMinViaOuter = N
rlMaxViaOuter = N
rlMinViaInner = N
rlMaxViaInner = N
rlMinMicroViaOuter = N
rlMaxMicroViaOuter = N
rlMinMicroViaInner = N
rlMaxMicroViaInner = N
psTop = N
psBottom = N
psFirst = N
psElongationLong = N
psElongationOffset = N
mvStopFrame = N
mvCreamFrame = N
mlMinStopFrame = N
mlMaxStopFrame = N
mlMinCreamFrame = N
mlMaxCreamFrame = N
mlViaStopLimit = N
srRoundness = N
srMinRoundness = N
srMaxRoundness = N
slThermalIsolate = N
slThermalsForVias = N
dpMaxLengthDifference = N
dpGapFactor = N
checkGrid = N
checkAngle = N
checkFont = N
checkRestrict = N
useDiameter = N
maxErrors = N

Each line in the DRU file represents a specific design rule, with the format ruleName = value. The value can be a numeric value or a string, depending on the rule.

New Features in CadSoft EAGLE DRU Files for EAGLE V6

CadSoft EAGLE V6 introduces several new features and enhancements to the DRU files, providing more control and flexibility over the PCB design process. Let’s explore some of the key new features:

1. Enhanced Layer Setup

EAGLE V6 DRU files now offer an enhanced layer setup section, allowing you to define the layer stack of your PCB more accurately. The layerSetup rule enables you to specify the number of copper layers, their names, and the order in which they appear in the layer stack.

Example:

layerSetup = (1*16)

In this example, the PCB has 16 layers, with the top layer being layer 1 and the bottom layer being layer 16.

2. Improved Clearance Rules

The new DRU files provide more granular control over clearance rules, enabling you to define minimum clearances between various types of objects on the PCB. The following clearance rules are available:

• mdWireWire: Minimum clearance between two wires
• mdWirePad: Minimum clearance between a wire and a pad
• mdWireVia: Minimum clearance between a wire and a via
• mdPadPad: Minimum clearance between two pads
• mdPadVia: Minimum clearance between a pad and a via
• mdViaVia: Minimum clearance between two vias
• mdSmdPad: Minimum clearance between an SMD pad and a pad
• mdSmdVia: Minimum clearance between an SMD pad and a via
• mdSmdSmd: Minimum clearance between two SMD pads

Example:

mdWireWire = 8mil
mdWirePad = 8mil
mdWireVia = 8mil
mdPadPad = 8mil
mdPadVia = 8mil
mdViaVia = 8mil
mdSmdPad = 8mil
mdSmdVia = 8mil
mdSmdSmd = 8mil

These rules ensure that the PCB layout maintains proper clearances between different objects, reducing the risk of short circuits and improving manufacturability.

3. Via and Microvia Rules

EAGLE V6 DRU files introduce new rules for vias and microvias, allowing you to define their dimensions and constraints more precisely. The following via and microvia rules are available:

• rvPadTop: Restring via pad size on the top layer
• rvPadInner: Restring via pad size on inner layers
• rvPadBottom: Restring via pad size on the bottom layer
• rvViaOuter: Restring via hole size for outer layers
• rvViaInner: Restring via hole size for inner layers
• rvMicroViaOuter: Restring microvia hole size for outer layers
• rvMicroViaInner: Restring microvia hole size for inner layers
• rlMinPadTop: Minimum via pad size on the top layer
• rlMaxPadTop: Maximum via pad size on the top layer
• rlMinPadInner: Minimum via pad size on inner layers
• rlMaxPadInner: Maximum via pad size on inner layers
• rlMinPadBottom: Minimum via pad size on the bottom layer
• rlMaxPadBottom: Maximum via pad size on the bottom layer
• rlMinViaOuter: Minimum via hole size for outer layers
• rlMaxViaOuter: Maximum via hole size for outer layers
• rlMinViaInner: Minimum via hole size for inner layers
• rlMaxViaInner: Maximum via hole size for inner layers
• rlMinMicroViaOuter: Minimum microvia hole size for outer layers
• rlMaxMicroViaOuter: Maximum microvia hole size for outer layers
• rlMinMicroViaInner: Minimum microvia hole size for inner layers
• rlMaxMicroViaInner: Maximum microvia hole size for inner layers

Example:

rvPadTop = 24mil
rvPadInner = 24mil
rvPadBottom = 24mil
rvViaOuter = 8mil
rvViaInner = 8mil
rvMicroViaOuter = 4mil
rvMicroViaInner = 4mil
rlMinPadTop = 20mil
rlMaxPadTop = 28mil
rlMinPadInner = 20mil
rlMaxPadInner = 28mil
rlMinPadBottom = 20mil
rlMaxPadBottom = 28mil
rlMinViaOuter = 6mil
rlMaxViaOuter = 10mil
rlMinViaInner = 6mil
rlMaxViaInner = 10mil
rlMinMicroViaOuter = 3mil
rlMaxMicroViaOuter = 5mil
rlMinMicroViaInner = 3mil
rlMaxMicroViaInner = 5mil

These rules define the dimensions and constraints for vias and microvias, ensuring that they meet the manufacturing requirements and maintain proper connectivity.

4. Solder Mask and Paste Mask Rules

The new DRU files offer more control over solder mask and paste mask settings. You can define the solder mask expansion, paste mask shrinkage, and other related parameters using the following rules:

• psTop: Solder mask expansion on the top layer
• psBottom: Solder mask expansion on the bottom layer
• psFirst: Paste mask shrinkage on the first paste layer
• psElongationLong: Elongation for long pads
• psElongationOffset: Elongation offset for long pads
• mvStopFrame: Minimum solder stop mask width
• mvCreamFrame: Minimum cream frame width
• mlMinStopFrame: Minimum solder stop mask frame width
• mlMaxStopFrame: Maximum solder stop mask frame width
• mlMinCreamFrame: Minimum cream frame width
• mlMaxCreamFrame: Maximum cream frame width
• mlViaStopLimit: Via solder stop mask limit

Example:

psTop = 4mil
psBottom = 4mil
psFirst = -4mil
psElongationLong = 100mil
psElongationOffset = 50mil
mvStopFrame = 1.5mm
mvCreamFrame = 0.1mm
mlMinStopFrame = 4mil
mlMaxStopFrame = 20mil
mlMinCreamFrame = 0mil
mlMaxCreamFrame = 20mil
mlViaStopLimit = 25mil

These rules help you achieve the desired solder mask and paste mask coverage, ensuring proper solderability and preventing short circuits.

5. Roundness and Thermal Relief Rules

EAGLE V6 DRU files introduce new rules for controlling the roundness of pads and thermal relief settings. The following rules are available:

• srRoundness: Roundness of pads and vias
• srMinRoundness: Minimum roundness of pads and vias
• srMaxRoundness: Maximum roundness of pads and vias
• slThermalIsolate: Thermal isolation for pads
• slThermalsForVias: Thermal relief for vias

Example:

srRoundness = 0
srMinRoundness = 0
srMaxRoundness = 0
slThermalIsolate = 10mil
slThermalsForVias = 1

These rules allow you to control the shape of pads and vias and define thermal relief settings to improve solderability and heat dissipation.

Benefits of Using CadSoft EAGLE DRU Files

Using CadSoft EAGLE DRU files offers several benefits for PCB designers:

1. Consistency: DRU files ensure that your PCB designs adhere to a consistent set of design rules, reducing the risk of errors and improving overall quality.

2. Manufacturability: By defining appropriate design rules, you can ensure that your PCB layouts are manufacturable and meet the required specifications.

3. Efficiency: DRU files automate the design rule checking process, saving time and effort in identifying and resolving design rule violations.

4. Customization: You can create custom DRU files tailored to your specific design requirements, providing flexibility and control over the PCB design process.

5. Collaboration: DRU files can be shared among team members, ensuring that everyone follows the same design rules and maintains consistency across projects.

Best Practices for Using CadSoft EAGLE DRU Files

To make the most of CadSoft EAGLE DRU files, consider the following best practices:

1. Choose the right DRU file: Select a DRU file that matches your PCB fabrication capabilities and design requirements. EAGLE provides several pre-defined DRU files, but you can also create custom ones.

2. Customize DRU files as needed: Modify the DRU file to suit your specific design needs. Adjust the values of the design rules based on your PCB manufacturer’s specifications and your own design preferences.

3. Run DRC regularly: Perform Design Rule Checks (DRC) frequently during the PCB design process to identify and resolve any rule violations early on. This helps avoid costly mistakes and saves time in the long run.

4. Document your DRU files: Maintain clear documentation of your DRU files, including the purpose, settings, and any modifications made. This helps other team members understand and use the DRU files effectively.

5. Keep DRU files up to date: Regularly review and update your DRU files to reflect changes in manufacturing capabilities, design standards, or project requirements. Ensure that all team members are using the latest version of the DRU file.

Frequently Asked Questions (FAQ)

1. What is a CadSoft EAGLE DRU file?
   A CadSoft EAGLE DRU file is a plain text file that contains a set of design rules for PCB layouts. It defines constraints and requirements for various aspects of the PCB design, such as minimum trace width, clearances, drill sizes, and more.

2. Why are DRU files important in PCB design?
   DRU files are important because they help ensure that PCB designs are manufacturable and meet the required specifications. By adhering to the design rules defined in the DRU file, designers can avoid common mistakes and create high-quality PCB layouts.

3. What are the new features introduced in CadSoft EAGLE DRU files for EAGLE V6?
   CadSoft EAGLE V6 introduces several new features in DRU files, including enhanced layer setup, improved clearance rules, via and microvia rules, solder mask and paste mask rules, and roundness and thermal relief rules. These features provide more control and flexibility over the PCB design process.

4. How do I create a custom DRU file in CadSoft EAGLE?
   To create a custom DRU file in CadSoft EAGLE, follow these steps:

5. Open the EAGLE Control Panel and navigate to the “DRU” folder.
6. Right-click in the folder and select “New” to create a new DRU file.
7. Give the DRU file a meaningful name and save it.
8. Open the DRU file in a text editor and define your desired design rules using the appropriate syntax.

9. Save the DRU file and select it in the EAGLE Board Editor when running Design Rule Checks.

10. Can I share CadSoft EAGLE DRU files with other team members?
    Yes, you can share CadSoft EAGLE DRU files with other team members. Sharing DRU files ensures that everyone follows the same design rules and maintains consistency across projects. Simply provide the DRU file to your team members and ensure that they use it when designing PCB layouts in EAGLE.

Conclusion

CadSoft EAGLE DRU files are essential for creating high-quality and manufacturable PCB designs. The new features introduced in CadSoft EAGLE DRU files for EAGLE V6 offer enhanced capabilities and improved design rule management, empowering designers to create more reliable and efficient PCB layouts.

By understanding the structure and rules available in DRU files, customizing them to suit your design requirements, and following best practices, you can leverage the full potential of CadSoft EAGLE and streamline your PCB design process. Regularly running Design Rule Checks and keeping your DRU files up to date ensures that your PCB designs meet the highest standards of quality and manufactur